San Francisco 49ers free safety Eric Reid (35) looks up at the scoreboard as he sits on the bench during the second quarter of an NFL football preseason game against the Houston Texans Thursday, Aug. 28, 2014, in Houston.
David J. Phillip
AP

Defensive line

This deep group was supposed to be the defense’s strength. And while it hasn’t been an obvious weakness, the 49ers have been pushed around at times by the opponent’s running attack and rank 20th in run defense. They also have allowed six rushing touchdowns; only the Atlanta Falcons, who have given up seven rushing touchdowns, are worse. The 49ers used to be a top-five team stopping the run, and their decline underscores their offseason losses, which included defensive lineman Justin Smith and inside linebacker Patrick Willis. First-round pick Arik Armstead has been a bright spot because he’s consistently broken down the passer’s pocket. The 49ers, however, have limited Armstead’s snap count. Grade: C-

Linebacker

NaVorro Bowman clearly is not back to his pre-injury form, although his leadership and grit make him invaluable. On Tuesday, the 49ers traded for linebacker Gerald Hodges, which says something about how they feel about Michael Wilhoite, who started the first four games. On the outside, Ahmad Brooks and Aaron Lynch were much more effective when they were assigned to go after the quarterback and not cover receivers. Behind them, however, Corey Lemonier doesn’t offer much pop and rookie Eli Harold needs to add some bulk to his lanky frame. The 49ers worked out one-time draft pick Parys Haralson on Monday. Grade: C

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Cornerback

First-year starter Kenneth Acker has shown nice pluck and confidence through four games, but he clearly is being targeted. According to Pro Football Focus, he has given up 303 passing yards through four games. Of 104 cornerbacks analyzed, only one – the Philadelphia Eagles’ Byron Maxwell – has allowed more. The flip side is teams mostly are staying away from fellow starter Tramaine Brock, although he had issues against the Pittsburgh Steelers and Arizona Cardinals, too. Dontae Johnson was perhaps the lone member of the secondary who played well against the Cardinals in Week 3, and Keith Reaser had a solid stint as a linebacker against the Green Bay Packers. Which cornerbacks enter games – and when – will be based on matchups. Grade: C-

Safety

Opponents have a 108.3 passer rating against the 49ers, fourth worst in the league. That reflects the team’s safeties and the overall scheme, which obviously is not using that group’s skills – or hiding its deficiencies – as well as the previous scheme. Antoine Bethea is smart and experienced, but he’s not fast and has been burned deep at least twice. Eric Reid has four missed tackles and no interceptions or pass defenses. He’s taken some bizarre angles on would-be tackles and was fooled by a pump fake by Green Bay’s Aaron Rodgers, even though Rodgers was six yards beyond the line of scrimmage and no longer a threat to throw. On the plus side, Jimmie Ward and Jaquiski Tartt have looked good in substitute packages, but their playing time vacillates from week to week. There’s a sense the defense should figure out which combinations work best and stick with them. Grade: C-

Punter

Bradley Pinion has done a decent job, including landing eight punts inside the opponent’s 20-yard line. But he’s been a bit inconsistent and his early performance doesn’t explain why the team parted with veteran Andy Lee, who leads the league in gross (52.7 yards) and net (47.4) average for the Cleveland Browns. Pinion’s net average (41.5) is tied for 13th in the league. He gets extra points for handling kickoffs. Grade: B